Cell cultures, whether homogeneous or not (cocultures), may be useful models for some genetic, biochemical, metabolic or physiological processes that take place within the living organism. Their ease of use allows a large number of conditions to be analysed before performing the definitive experiments on animals or clinical tests on human beings. In vitro models are a tool for validating new therapeutic targets, to select seeds in high-performance systems, to define the mechanism of action of new molecules and, in general, for biomedical, biotechnological or cosmetic research.
In general, all models based on cell cultures have a limited useful life. Thus, culture cells pass through different differentiation phases, and require continuous manipulation to maintain the properties that make them a suitable model. For example, the gastrointestinal barrier model based on the confluent culture of Caco-2 cells requires 21 days to reach the state of differentiation which allows many of the properties of intestinal mucous to be reproduced (Le Ferrec et al., ATLA 29:649-668, 1999), and its use is prolonged only during a window of approximately 3 to 5 days. BC2 cells, used as a model of hepatic cell, require between three and four weeks of differentiation before they acquire the properties that make them a good model, and the subsequent culture conditions are essential for them to respond to the experimental treatments in a similar way to hepatocytes (M J Gómez Lechón et al., Eur. J. Biochem. 268:1448, 2001). Huvec umbilical cord cells, grown to confluence, may be induced to form structures comparable to blood veins in suitable experimental conditions, for which reason they constitute a good model of angiogenesis (Vailhe et al., Lab. Invest. 81:439-452, 2001), Nevertheless, the number of cell divisions prior to the experiment and the stimulus used are critical to obtaining a suitable response.
These limitations in the manipulation and generation of the different in vitro cell models make them difficult to implement for occasional users, and in general limit the marketing of the models in their end format. The problem gets worse in complex models, wherein the cells should imitate the organism's natural barriers (Rubas et al., J. Pharma. Sci., 85:165-169, 1996; Walter et al., J. Pharma Sci., 85:1070-1076; Irvine et al., J. Pharma Sci., 88:28-33, 1999; Gaillard et al., Eur. J. of Pharma Sci., 12:215-222, 2001); or the cultures should be performed on asymmetric supports, separating two compartments or with a strong dependence on the polarisation of the system components. In these cases, to the complexity of the model and its time limits, we can add mechanical-type problems, which mean bumps or shaking may invalidate the system. Researchers can access the different model components (support, culture medium and additives and cell lines) and later they should combine them in the laboratory using more or less laborious processes). In the best of the cases, the final researcher may receive the cells ready-for-use, but with limitations which practically mean it is obligatory to perform the experiments within two days after their reception, and they impose serious restrictions on the distribution of the model by the company marketing it, such as, for example, In Vitro Technologies. Document EP 702 081 discloses a method for the storage and transport of three-dimensional tissues which consists of positioning said three-dimensional tissue fixed on two types of sponges in a gelatine solution, so that this gels with cooling, thus making it easier to transport and store.
Therefore, there is an existing need in the state of the art for providing a method to be able to supply models based on ready-to-use organized two-dimensional cell cultures and with their functional properties intact so that, on the one hand, the researcher has a margin of manoeuvre for its use and, on the other, the supplying company may consider delivery times within the reasonable logistic margins of international distribution.
The object of the present invention consists of providing a method of storing and transporting in vitro organized two-dimensional cell cultures which resolves the aforementioned needs of the state of the art.